Inorganic-Organic Hybrid Polyoxoniobates: Polyoxoniobate Metal Complex Cage and Cage Framework

The combination of polyoxoniobates (PONbs) with 3d metal ions, azoles, and organoamines is a general synthetic procedure for making unprecedented PONb metal complex cage materials, including discrete molecular cages and extended cage frameworks. By this method, the first two PONb metal complex cages K-4@{[Cu-29(OH)(7)(H2O)(2)(en)(8)(trz)(21)][Nb24O67(OH)(2)(H2O)(3)](4)} and [Cu(en)(2)]@{[Cu-2(en)(2)(trz)(2)](6)(Nb68O188)} have been made. The former exhibits a huge tetrahedral cage with more than 120 metal centers, which is the largest inorganic-organic hybrid PONb known to date. The later shows a large cubic cage, which can act as building blocks for cage-based extended assembly to form a 3D cage framework {[Cu(en)(2)]@{[Cu-2(trz)(2)(en)(2)](6)[H10Nb68O188]}}. These materials exhibit visible-light-driven photocatalytic H-2 evolution activity and high vapor adsorption capacity. The results hold promise for developing both novel cage materials and largely unexplored inorganic-organic hybrid PONb chemistry.